Temperature Dependence of the CdS Bandgap in the Extreme Confinement Regime.
basic_science · Level V
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- Record sourced from PubMed, PMID 37811888.
- Also identified by DOI 10.1021/acs.nanolett.3c02368.
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Abstract
A non-empirical equation describing the effect of size on the temperature dependence of the optical bandgap of CdS (d<i>E</i><sub>g</sub>/d<i>T</i>) is obtained on the basis of the Brus equation. Intriguingly, we find that d<i>E</i><sub>g</sub>/d<i>T</i> diverges strongly from bulk values only within the "extreme confinement" (EC) regime. We conducted both experimental and theoretical investigations of the absorption spectra of CdS clusters and quantum dots as a function of temperature above room temperature. Our results show that the value of d<i>E</i><sub>g</sub>/d<i>T</i> obtained from absorption spectra in the EC regime is 2.5 times higher than in the strong confinement regime. Notable ligand sensitivities are also observed for d<i>E</i><sub>g</sub>/d<i>T</i> in the case of CdS clusters. <i>Ab initio</i> molecular dynamics simulations and density functional theory calculations reveal that thermal fluctuations are the crucial factor influencing the bandgap temperature coefficient. Our results help resolve some long-standing debates regarding the d<i>E</i><sub>g</sub>/d<i>T</i> behavior of semiconductor quantum dots.